The invention relates to a device for puffing foodstuffs, especially cereals and pulse, in an upright puffing reactor comprising a vessel that can be closed for receiving the foodstuff as a granular product, further a supply line for introducing a pressurized, heat-carrying agent into the vessel, and an opening mechanism for the abrupt opening of the vessel. The present invention further relates to a method for puffing foodstuffs, especially cereals and pulse, where the foodstuff is processed to the state of a granular product, the product is then placed in a closed, upright vessel, is subjected in the closed vessel to the action of a pressurized, heat-carrying agent in a manner such that when subsequently the vessel is opened, an abrupt pressure reduction occurs, with the product being expelled from the vessel, such that the product is puffed out.
A device and a method of that kind have been known from EP 0 061 229 B1.
The term puffing describes a processing method for cereals and pulse, where the product is steamed and, after release of the pressure, puffed out to form light masses. The product is then sold as puffed wheat, puffed rice, puffed corn, puffed peas, etc.
In the thirties of this century, the respective installations were designed in such a way that the product is introduced into a lying cylinder through a charging box, whereafter the cylinder is closed by a special device. The cylinder is then set to rotate and is heated by gas flames until the pressure in the cylinder has reached a predetermined level. Thereafter steam is introduced into the cylinder until the steam pressure reaches a predetermined value. The steam supply is then shut off, and heating by the gas flames is continued until a pressure of approximately 12 bar prevails inside the cylinder. Now the internal pressure is abruptly released by blowing open and/or opening the door of the cylinder, which is especially designed for this purpose. The product shoots out of the cylinder, and exactly at that moment the product expands and increases its volume so as to form the puffed product. The core of the product had already been softened under the action of the steam, and the high steam pressure of 12 bar already prevails in its interior. At the moment the cylinder is discharged, the outer pressure suddenly disappears, and the high pressure still prevailing inside the grain puffs the grain structure, which means that the grain is expanded to eight times to ten times its original size. Opening the cylinder is accompanied by a gun-like detonation, which also releases corresponding recoil forces. The flap or the closure of the cylinder is designed as an end flap of the lying cylinder, which is exposed to extremely high loads. It often happened that the flap was torn off the cylinder together with the entire mounting mechanism.
Certain further developments then led to installations where the discharge openings were provided at the bottom.
The previously mentioned European Patent Specification No. EP 0 061 229 now comprises an upright, approximately cylindrical vessel which is filled with the product from above and is then closed. In the lower end portion, which also comprises the discharge end, a pressurized, heat-carrying agent is introduced into the vessel via a single line. The pressurized, heat-carrying agent so introduced--in most cases pressurized steam--flows through the product or material in the vessel, thus heating it up to the desired temperature. According to EP 0 061 229 B1, the heating process is continued until a temperature of between 100.degree. and 300.degree. Celsius is reached, whereby a pressure of at least 5 bar is built up. The lower end of the vessel is provided with a discharge line, which is bent off by 90.degree. and which opens into an expansion chamber. Under the selected conditions, the humidity contained inside the product, originating either from the product itself or from a corresponding pretreatment of the product, is likewise heated up, without however vaporizing. When the opening mechanism is opened, the product shoots out of the vessel through the discharge line, and expands in the expansion chamber, i.e. the abrupt pressure reduction also allows the humidity contained in the product to vaporize abruptly, whereby the product is puffed.
The device and the method described in EP 0 061 229 are, however, connected with numerous disadvantages.
The agent which is introduced into the vessel at a temperature of 200.degree. to 300.degree. Celsius is so hot that the product presents a risk of damage or burns.
In addition, it costs a lot of energy to heat water steam up to such high temperatures.
In the lower third of the filled reactor, a lot of condensation occurs with the effect that the product gets excessively wet and that the subsequent expansion process leads to a poor result. In the upper third of the reactor, the product is heated up and wetted insufficiently, which also leads to a poorly puffed product.
EP 0 437 295 A1 discloses a reactor with a perforated vessel received in its interior. The agent (for example water vapor) is permitted to flow from the outside through the perforations and into the product contained in the vessel, and to heat it up.
Now, it is the object of the present invention to improve a device and a method of the before-mentioned kind in such a way as to permit the product to be treated with relatively low temperatures, while achieving an expulsion pressure that normally would require higher temperatures.